JPH0730294B2 - High-speed bonding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-speed bonding method for bonding paper at high speed.

(Prior Art) As a high speed adhesive, particularly a high speed adhesive for paper, a homo- or copolymer-based aqueous emulsion of vinyl acetate is mainly used. This water-based emulsion adhesive does not have the problems of environmental pollution and fire like solvent-based adhesives, but the initial drying of the adhesive force is slow due to the low drying rate of water in the emulsion, and the mechanical suitability, especially the flow characteristics, is also low. Is insufficient. Therefore, there are various problems to be solved when used in recent high-speed bonding machines.

Generally, in high-speed mechanical bonding, initial adhesiveness and mechanical suitability are important. The initial adhesiveness mainly depends on the rate of increase in viscosity by which water evaporates to increase wet tack and the rate of film formation at which emulsion particles start to fuse and form a film. It varies depending on the amount and the emulsion concentration, and further on the kind and the amount of the additive such as a plasticizer and a solvent to be added. On the other hand, mechanical suitability, that is, characteristics of an adhesive required when used in a high-speed bonding machine include, for example, viscosity, flow characteristics, stability, non-foaming property, and rust prevention property. As described above, since there are many factors that influence the performance of the high-speed adhesive and the factors are related to each other, various theories of adhesion suitability have been proposed, but none of them are perfect. Therefore, the present condition is to find the optimum conditions based on experiments.

To date, various compositions have been developed and put into practical use as high-speed adhesives, but in order to increase the production speed, adhesives having higher-speed adhesive properties are required. Especially with cigarette chip paper attachment, more than 4,000 pieces per minute,
That is, a linear velocity of about 10 m / min or more is required. However, conventional adhesives cannot satisfy this required performance. That is, in the high-speed adhesive machine as described above, the rotation speed of the coating roll is extremely large, and the shearing force applied to the adhesive becomes large, but the conventional emulsion-type adhesive has a reduced viscosity under high shearing force.
So-called tack does not appear, initial adhesive strength is insufficient, and roll workability is poor. In addition, the paper to be pre-deposited has become thinner and has increased air permeability, so in order to develop the initial adhesive strength, the moisture in the emulsion is allowed to penetrate into the adherend such as paper to fuse the polymer particles to each other. There is a limit in the method of (drying).

(Object of the invention) Therefore, an object of the present invention is to provide a high-speed bonding method that satisfies both the initial adhesiveness and mechanical properties, and in particular, a thin paper with a large air flow rate at a linear velocity of about 10 m / min or more. The present invention relates to a high-speed bonding method suitable for mechanical bonding at high speed.

(Structure of the Invention) The present inventor found that the most important factor in the synthetic resin emulsion adhesive used for high-speed adhesion, particularly for high-speed adhesion at a linear velocity of about 10 m / min or more is its flow property, and various experiments were conducted. As a result of the above, it was found that high-speed adhesion can be achieved by using an adhesive containing a vinyl acetate-based emulsion having specific dirant flow characteristics, and the present invention was completed.

The present invention is characterized in that an aqueous vinyl acetate emulsion contained in an adhesive is polymerized by adding a phthalate ester to a heated emulsion polymerization system, an acrylic acid alkyl ester, a maleic acid dialkyl ester, and a (meth) acryl. An emulsion obtained by adding an acid to an emulsion polymerization system for polymerization, or a vinyl acetate-based aqueous emulsion containing polyvinyl alcohol, and an inorganic electrolyte that functions as a gelling agent for polyvinyl alcohol. 6 rpm using rotor No.3 of viscometer
Viscosity η (6) measured at 60 rpm and viscosity η (6
0) and the viscosity ratio η (6/60) is 0.8 ≦ viscosity ratio η (6/60) <1, the point of using an adhesive having dilatant flow characteristics, and linear velocity of about 10 m / min. The point is to bond the paper at the above speed.

Before describing the present invention, first, the flow characteristics of the synthetic resin emulsion will be briefly described. In general, emulsions are non-Newtonian, which have two flow characteristics: pseudoplastic flow, in which the apparent viscosity decreases with increasing shear rate, and conversely, dilatant flow, with which the apparent viscosity increases with increasing shear rate. Can be roughly divided into those that indicate. Relatively high concentration, high viscosity emulsions such as those used in adhesives generally exhibit pseudoplastic flow. The phenomenon in which the viscosity shows a time-dependent isothermal plasticity decrease is generally called thixotropy, which corresponds to the above pseudoplastic flow.

In this way, the viscosity behavior when the viscosity changes due to the change in shear rate is called structural viscosity, and in order to express the degree of this structural viscosity, the rate of change in viscosity with respect to change in shear rate is taken as the structural viscosity index. When the B-type viscometer is used, the rotor is determined at a constant temperature, the viscosity (η) and the rotor rotational speed (ω) are logarithmic, and the rate of change (b) is used as the structural viscosity index. That is, these relationships are represented by the following formula (1).

logη = loga + blogω (1) For convenience, use rotor No.3 of B-type viscometer at 6 rpm and 60
When measured with rpm, the ratio (6/60) of each viscosity η (6) and η (60) is used. If this value is less than 1, dilatancy, 1 if it is Newtonian, and if it exceeds 1 It can be said to be thixotropy.

In the present invention, the above-mentioned structural viscosity index (b) is positive, that is, it has dilatant flow characteristics, and other adhesive characteristics such as the above-mentioned initial adhesiveness and other mechanical characteristics are maintained at the same level or more as those of conventional adhesives. The above vinyl acetate emulsion is used as a high-speed adhesive.

Conventionally, several synthetic resin emulsions showing dilatant flow characteristics have been reported in the process of studying the physical properties of emulsions, for example, when a high solid content emulsion of a hard polymer such as polystyrene or polymethacrylate is prepared using a small proportion of emulsifier. Etc.

However, it is obvious that even if it has only dilatant flow characteristics, it cannot be used as a high-speed adhesive unless the initial adhesiveness and mechanical characteristics are satisfied.

The inventors of the present invention have found that if an adhesive having improved flow characteristics and dilatant flow characteristics is used while maintaining the adhesive strength of conventional adhesives, various requirements can be satisfied and high-speed adhesion can be achieved.

In the method of the present invention, an adhesive containing at least one of vinyl acetate homopolymer aqueous emulsion and vinyl acetate copolymer aqueous emulsion is used. The vinyl acetate copolymer-based aqueous emulsion also includes an ethylene-vinyl acetate copolymer-based aqueous emulsion.

This adhesive has dilatant flow properties with 0.8 ≦ viscosity ratio η (6/60) <1. If the viscosity ratio is out of the above range, it becomes difficult to bond the paper at a linear velocity of about 10 m / min or more.

The method of the present invention is mainly used for adhering paper, but is particularly useful for adhering thin paper having a large air flow rate.

The adhesive containing the vinyl acetate-based aqueous emulsion having the above-mentioned fluidity while maintaining the adhesive strength can be obtained by 1) a method by polymerization and 2) a method by a composition at the time of polymerization and / or compounding.

More specifically, as a method for obtaining the adhesive having the dilatant property, a phthalate ester is added to a heated emulsion polymerization system for polymerization, an alkyl acrylate ester, a dialkyl maleate ester, (meth) A method in which acrylic acid is added to an emulsion polymerization system to carry out polymerization is mentioned.

As a method of obtaining the adhesive having the dilatant property depending on the composition, a method of adding an inorganic electrolyte to the vinyl acetate-based aqueous emulsion can be mentioned. In particular,
When a polymer having a hydroxyl group such as polyvinyl alcohol is present, a deol type intramolecular and / or intermolecular crosslink is generated between the inorganic electrolyte and the hydroxyl group, whereby the dilatant property can be exhibited.

As the above-mentioned inorganic electrolyte, those known as gelling agents for Poval, for example, Na ₂ SO ₄ , sulfates of monovalent metals such as (NH ₄ ) SO ₄ , nitrates such as NH ₄ NO ₃ , Na ₃ PO _4, etc. Examples thereof include phosphates, organic salts such as potassium citrate, boric acid, and borax.

The amount of these inorganic electrolytes added depends on the type of emulsion. The emulsion to which the inorganic electrolyte is added may or may not be dylanic in itself.

In addition, the adhesive may contain a defoaming agent, an antiseptic, and the like.

The relationship between the adhesive having the dilatant flow characteristics and the high-speed adhesion characteristics will be described below.

The performance of the adhesive used in the high-speed adhesive machine is the initial adhesiveness,
There are a number of roll leveling properties, storage stability, re-emulsifying properties, etc., but in order to comprehensively evaluate these, we actually tested using a high-speed adhesive that is actually used, and the resulting adhesion failure rate and roll It is sure to check workability.

Since it is the cigarette tip attachment machine that requires high-speed adhesion at a linear velocity of about 10 m / min or more today, this machine can be used to evaluate the high-speed adhesion characteristics as follows.

1) Measurement of adhesion defect rate The number of defective products when the chip paper is wrapped around 4000 cigarette filter chips per minute and the porous paper is adhered using the tobacco chip attachment (MMC-4000 x 10000 ml machine) that can adhere. Is expressed as the number per 100,000 pieces (unit: number).

2) Measurement of roll workability The amount of adhesive scattered when the adhesive winding roll and the adhesive coating roll are adhered to each other and rotated in the opposite direction at 330 rpm for 30 minutes Attach to foil and weigh the amount (unit: mg).

Based on the measurement results of 1) and 2) above, the adhesive performance index (F) (unit: book × mg) of the adhesive can be determined by the following formula.

Adhesive figure of merit (F) = adhesion failure rate × scattering amount Then, when high-speed adhesion was performed using an adhesive having various viscosity ratios η (6/60), the results shown in FIG. 1 were obtained.

FIG. 1 shows the relationship between the adhesive performance index and the η (6/60). As is clear from this figure, as the adhesion speed increases, 0.8 ≦ viscosity ratio η (6/60) <
It can be seen that an adhesive having a dilatant structural viscosity of 1 is suitable.

(Effects of the Invention) According to the method of the present invention, even thin paper having a large ventilation amount can be bonded at high speed.

(Example) Hereinafter, the present invention will be described in more detail based on examples.

Example 1 In a four-necked flask with an internal capacity of 1 equipped with a thermometer, a stirrer, a cooler, a dropping funnel, etc., 123.5 parts of deionized water (parts by weight, hereinafter the same), 100 parts of vinyl acetate, polyvinyl alcohol at room temperature. (Saponification degree 95%, molecular weight 600-1700) Add 8.5 parts, raise the temperature with stirring, add 0.2 parts of hydrogen peroxide when reaching 70 ° C, and maintain at 80 ° C and polymerize for 2 hours. After 2 hours, dibutyl phthalate (DB
15 parts of P) was added dropwise over 1 hour. The emulsion was then aged at 85 ° C for 2 hours.

The viscosity of the obtained emulsion was measured with a B-type viscometer (rotor N
o.3). The apparent viscosity ratio η (6/60) was 0.9 when measured at rotation speeds of 6 rpm and 60 rpm. The adhesion failure rate (D) of this emulsion was 49.6. The defective adhesion rate is represented by the number of defective articles per 100,000 when they are adhered using a cigarette attachment machine having a production capacity of 4000 pieces / minute.

Example 2 The same apparatus as in Example 1 was charged with 125 parts of deionized water and polyvinyl alcohol (saponification degree: 95 mol% and 92 mol%).
(1: 1 mixed) 10 parts, and after heating, add potassium persulfate and, while maintaining at 80 ° C, first add 33 parts of vinyl acetate dropwise over the first 60 minutes, and then for 2 hours. Then, 67 parts of vinyl acetate and 15 parts of dibutyl phthalate are added dropwise to carry out polymerization. After that, aging was carried out at 85 ° C. for 2 hours.

The obtained emulsion had an η (6/60) of 0.9 and an adhesion failure rate of 50.

Comparative Example 1 The same operation as in Example 1 was carried out without adding dibutyl phthalate during the polymerization. In this case, η (6/60) is 1.3
And the adhesion failure rate (D) was 600.

Comparative Example 2 The same operation as in Comparative Example 1 was carried out, except that (1) dibutyl phthalate was added after the emulsion reached room temperature during the polymerization, and (2) the emulsion was further heated at 80 ° C.
After the temperature was raised again up to, dibutyl phthalate was added. However, both η (6/60) was 1.2, and the adhesion failure rate was 700.

Example 3 Using the same apparatus as in Example 1, 108.5 parts of deionized water and 8.5 parts of polyvinyl alcohol (saponification degree: 95 mol%) were heated to 70 ° C., and then 0.2 part of potassium persulfate was added, and further 80 parts were added. ℃
After heating to, vinyl acetate / dibutyl maleate (90: 1
0) 100 parts of the mixture are added over 2 hours and then 2 more
Aged for hours.

The obtained emulsion had η (6/60) of 0.89 and a defective adhesion rate of 90.

Examples 4 to 6 The procedure of Example 3 was repeated, except that dioctyl maleate (DOM), butyl acrylate (BA), and acrylic acid (AA) were used in place of the dibutyl malate of Example 3. The results obtained were as follows:

Example No. Additive component η (6/60) Adhesion failure rate 4 DOM 0.9 70 5 BA 0.9 110 6 AA 0.85 140 Example 7 An adhesive having the following composition was prepared using a vinyl acetate emulsion produced by a conventional method. did.

Vinyl acetate emulsion 69.22 parts Dibutyl phthalate 4.97 parts 15% Polyvinyl alcohol 11.06 parts (PVA-217) Defoamer (NOPCO-8034) 0.30 parts Preservative (slaoff-72N) 0.10 parts 5% H ₃ BO ₃ 5.60 parts 100.00 This adhesive The physical properties of the agent composition were as follows.

NV (nonvolatile) 48% Viscosity (Rotor No.3,30rpm) 1220CPS PH 4.6 PVA 15PHR DBP 30PHR The flow characteristics of this adhesive were η (6/60) = 0.95 and the adhesion failure rate was D = 100. .

[Brief description of drawings]

Fig. 1 shows 6rpm and 60rp using rotor No.3 of B type viscometer.
It is a figure showing the relationship between the ratio η (6/60) of each viscosity when measured in m and the adhesion coefficient of performance (F = adhesion failure rate × scattering amount) by changing the production rate of the cigarette chip attachment machine.

Claims (1)

[Claims] 1. A method for adhering paper using an adhesive containing at least one vinyl acetate aqueous emulsion selected from a vinyl acetate homopolymer aqueous emulsion and a vinyl acetate copolymer aqueous emulsion.
The vinyl acetate emulsion was polymerized by adding a phthalate ester to a heated emulsion polymerization system and polymerizing the emulsion, an alkyl acrylate ester, a dialkyl maleate ester, and (meth) acrylic acid were added to the emulsion polymerization system. An emulsion obtained by adding an inorganic electrolyte functioning as a gelling agent for polyvinyl alcohol to an emulsion or an aqueous vinyl acetate-based emulsion containing polyvinyl alcohol, which is a rotor for a B-type viscometer.
When the ratio of the viscosity η (6) measured at 6 rpm and the viscosity η (60) measured at 60 rpm using No. 3 is defined as the viscosity ratio η (6/60), 0.8 ≦ viscosity ratio η (6/60 ) A high-speed bonding method characterized in that a paper is bonded at a linear velocity of about 10 m / min or more using an adhesive having a dilatant flow characteristic of <1.